The present invention relates to polyoxymethylene fibers possessing high bend recovery, particularly monofilaments particularly useful as bristles in brushes of any kind.
Polyoxymethylene (hereinafter also referred to as “POM”) is a high-performance polymer possessing good mechanical properties and excellent chemical resistance. Shaped articles composed of POM are notable for high crystallinity and high modulus of elasticity.
POM fibers are also known that are notable for good mechanical properties, for example high strengths and high moduli of elasticity, and that are subjected after their production to drawing at a high draw ratio to fully actualize the potential of their material of construction.
DE-A-1 660 287 discloses a process for producing filaments of high molecular weight linear POM. The process comprises producing a spinning solution of a certain viscosity and dry- or wet-spinning this solution to form POM filaments which are subsequently subjected to a drawing operation on a hot iron. Typical draw ratios vary around 10:1.
JP 2001-172821 describes the production of POM fibers by melt spinning. The process comprises melting the raw material and spinning under defined conditions and also performing a drawing operation to at least 4:1 under defined incoming and outgoing speeds. The process is notable for high productivity and produces high-strength POM filaments.
EP-A-1,321,546 describes the production of high-strength and high-modulus POM split fibers. A film is produced using selected POM copolymers having defined viscosities. The choice of raw material makes it possible to control the rate of crystallization, allowing stable film formation and controlled drawing of the film.
EP-A-1,431,428 describes high-strength and high-modulus POM fibers. They are obtained by melt spinning using POM copolymers possessing a selected crystallization rate. Again, the choice of raw material allows controlled drawing to produce fibers having very high tensile strengths.
Prior art developments were directed to the production POM fibers possessing very high tensile strengths and moduli of elasticity. However, such fibers possess low elasticity and cross-directional strength, as manifested in low knot strength and poor recovery after bending or flexing.
Against this background, the present invention has for its object to provide fibers possessing excellent bend recovery.